Inkjet printing techniques are of increasing importance. In general, such techniques impose rigid requirements on ink compositions. Suitable inks for use in inkjet printing techniques are formulated with consideration of many different physical characteristics, including viscosity, resistivity, solubility, and wettabilty. The various components of the ink should be chemically compatible, relatively quick drying, and smear resistant. The ink composition should also minimize clogging of an inkjet nozzle and permit rapid clean-up of the inkjet machine components with minimum effort.
In addition to these factors, formulation of suitable inks should consider additional factors specific to a given application. The type of material to which the ink is applied and the environment in which the printed material is used will also affect the formulation of suitable inkjet inks. For example, printing symbols or words on the polymeric insulation of electrical wiring (e.g., cross-linked polyethylene) is often problematic. In order to protect the wiring from harsh environmental conditions (e.g., high temperatures and exposure to various chemicals such as gasoline, diesel, oil, antifreeze, and brake fluid), the polymeric insulation material is often chemically inert with a non-polar surface chemistry. Inks suitable for labeling the wires must both adhere to these polymeric insulation materials and be able to withstand the harsh environmental conditions. Currently, inkjet inks must undergo either or both a pretreatment process (e.g., those that use a corona, a plasma, or a flame) or post-treatment process (e.g., cross-linking the deposited inky with the use of thermal or UV radiation). Such pre- and post-treatments add processing steps that increase costs and productivity.
There exists a need for an ink that adheres to polymeric materials and leaves an identifiable indicia after exposure to harsh environmental conditions with fewer or no pre- and post-treatment processes.